242 J. CHEM. RESEARCH (S), 1999
J. Chem. Research (S),
1999, 242^243y
Organic Synthesis with Anion Exchange Resins:
Synthesis of a-Imino Nitriles from Nitronesy
Dilip Konwar,* Birendra Nath Goswami and Naleen Borthakur
Synthetic Organic Chemistry Division, Regional Research Laboratory, Jorhat-785 006, India
Nitrones react with amberlite IRA 400 [CN ] in acetonitrile to produce a-iminonitriles in good yield.
a-Iminonitriles are important intermediates for the synthesis
of a-amino acid derivatives and heterocyclic compounds.1;2
These compounds are prepared by reacting acetals with
isocyanates in presence of an AlClEt2 catalyst,3 reacting
dithioacetals with amines,4 re£uxing trimethyl silyl cyanide
(TMSCN) with bis-anils,2 oxidising conjugated imines with
chromic anhydrides in the presence of TMSCN,5 reacting
a-chloroimines with hydrogen cyanide6 and by reacting
cyanogen bromide with imines.7
In recent years anion exchange resins have been used in
many organic transformations. In continuation of our work
on anion exchange resin,8 we now report here the reaction
of amberlite IRA 400 [CN ] 2 with nitrones 1 to produce
a-imino nitriles. The reaction was carried out by stirring a
mixture of nitrones 1a ^ h and 2 in acetonitrile under re£ux.
The products 3a^h were obtained by simple ¢ltration, evap-
oration of the solvent under reduced pressure and
crystallization from appropriate solvents (Scheme 1). The
results are summarised in Table 1.
be stored for longer periods. (2) It does not require multi-step
synthesis, anhydrous conditions, and the product can be
obtained simply by ¢ltering out the resin and evaporating
o¡ the solvent.
+
R1
H
R1
NC
P
N[CN –
]
N
O
R2
N
R2
OH
H2O
H
+
N
–
P
OH
R1
–
+
A
+
+ H2O
OH N
P
N
R2
(P = polymer)
NC
Scheme 2
Experimental
The m.p.s. were measured in a Buchi apparatus and are uncorrected.
IR spectra were recorded on a Perkin-Elmer 237B spectrophotometer;
1H NMR spectra on aVarian T-60 spectrometer with TMS as internal
standard; and mass spectra on an AEIMS-30 spectrometer. The anion
exchange resin amberlite IRA 400 was purchased from Aldrich
chemicals as a chloride salt (16^60 mesh). The conversion of chloride
into cyanide was accomplished by following the literature procedure.9
The nitrones were prepared following a standard method.10
Preparation of a-Imino Nitriles.öIn a typical experiment a mixture of
a-phenyl-N-phenylnitrone (1a) (1.97 g, 0.01mol), acetonitrile (50 ml) and
amberlite IRA 400 [CN ] (10 ml, 0.01 equiv)9 was stirred magnetically
for 3 h in a 100 ml £ask at re£ux temperature. The reaction was moni-
tored by tlc. The resin was ¢ltered and the solvent distilled under
reduced pressure. The residue was crystallized from ethanol to obtain
3a, 1.89 g, 90%, m.p. 71 8C (lit, 72 8C4). Compounds 3b^h were pre-
pared in similar fashion (Table 1).
R1
H
R1
NC
2, Amberlite IRA 400 [CN–]
N
O
R2
N
R2
acetonitrile / reflux
1
3
Scheme 1
Regarding the mechanism of the reaction, it is proposed
that it proceeds via formation of a cyanohydroxylamine inter-
mediate A by taking a proton from the trace amount of water
present in the solvent which immediately loses a water mol-
ecule in presence of the HO
N
P resin formed in situ
(Scheme 2). In conclusion, we propose that it is a new
method for the preparation of a-imino nitriles using
amberlite IRA 400 [CN ] as cyanating agent. The reaction
has the following advantages over the existing methods:
(1) The polymer supported reagent is non-toxic and can
We acknowledge Dr J. C. S. Kataky, scientist, and Dr J. S.
Sandhu, Acting Director, regional research laboratory, Jorhat
for their encouragement and helpful suggestions.
Table 1 Synthesis of a-iminonitriles using amberlite IRA 400 [CN ]a
m.p./8C
found (lit.)
Entry
Product (3)
R1
R2
Yield(%)
Time/h
1
2
3
4
5
6
7
8
a
b
c
d
e
f
Ph
Ph
Me
C6H11
p-NO2-C6H4
m-NO2-C6H4
Ph
p-Br-C6H4
p-OMe-C6H4
90
80
75
78
82
76
77
81
3
3.5
4
3.6
4
6
71 (724)
p-Cl-C6H4
p-Me-C6H4
o-Cl-C6H4
p-NO2-C6H4
PhCH CH
PhCH CH
PhCH CH
50 (524)
67 (674)
117 (1164)
168 (1664)
72 (735)
g
h
5
5.5
141 (1425)
122 (1245)
aAll the compounds gave satisfactory IR, NMR, mass spectral and elemental analyses.
* To receive any correspondence.
y This is a Short Paper as de¢ned in the Instructions for Authors,
Received, 17th September 1998; Accepted, 2nd December 1998
Paper E/8/07253A
Section 5.0 [see J. Chem. Research (S), 1999, Issue 1]; there is
therefore no corresponding material in J. Chem. Research (M).
Konwar, Dilip
